Some of reflector-type vehicle lighting units can include a light source and a parabolic reflector having a focal point at or near the light source. Typical conventional light sources can adopt a bulb, but main stream has been to use a light emitting diode. This concept has been disclosed in Japanese Patent Application Laid-Open No. 2004-303639 or US2004/0252517A1, for example (which will be referred to as Patent Literature 1 hereinafter). A bulb can have an emission light source of a filament or a discharge unit, and can emit light from the emission light source radially in all directions. On the contrary, a light emitting diode can emit light with directionality. In other words, the optical axis of such a light emitting diode is directed in a direction in which the light emitting diode is disposed (directed). The light is radially emitted with the optical axis direction as a center, but no light is emitted in the opposite direction.
The vehicle lighting unit described in Patent Literature 1 includes one parabolic reflector (18) per one light emitting diode (16). The light emitting diode (16) is disposed at or near the focal point of the parabolic reflector (18) so that the light emitting diode is directed rightward when viewed from its front side. Thus, the light emission direction of the light emitting diode (16) is the right direction. Further, the parabolic reflector (18) is disposed so as to be spread from the light emitting diode (16) rightward. Since the light emitted from the light emitting diode (16) does not travel leftward, the parabolic reflector (18) is not provided on the left side of the light emitting diode (16) (on the side opposite to the light emitting direction of the light emitting diode (16)).
Even if the parabolic reflector (18) is provided with a leftward extending portion with respect to the light emitting diode (16) when viewed from its front side, the light emitted from the light emitting diode (16) can be reflected by the right portion of the parabolic reflector (18), but cannot be reflected by the left portion of the parabolic reflector (18). Accordingly, if the parabolic reflector (18) is provided with the left portion on the left side of the light emitting diode (16), when the parabolic reflector (18) is divided to right and left portions with respect to the vertical plane passing through the optical axis of the parabolic reflector (18), the left portion of the parabolic reflector (18) cannot be utilized effectively in a case where a single light emitting diode (16) is employed.